WASHINGTON — Weeks after the biggest national protest in U.S. history, a coalition of progressive grassroots organizers is planning a sequel — with the aim of pressuring President Trump to release his tax returns.

On April 15, the deadline for most Americans to file their 2016 returns, leaders from the Women’s March coalition and others, including MoveOn.org and the Indivisible Project, will hold a “Tax March” in Washington and at least 60 other locations. Those include New York, Los Angeles, Little Rock, Ark., and Boise, Idaho, organizers told USA TODAY.

Every U.S. president since Richard Nixon has released his tax returns. Demands for their release are gaining urgency after a Tuesday New York Times story that his campaign officials corresponded with Russian intelligence, the latest news story to draw connections between Trump and Russia, which U.S. intelligence agencies concluded attempted to help him win election.

Trump’s national security adviser, Michael Flynn, resigned Monday following reports that he lied about a December conversation with the Russian ambassador to the United States.

A number of news organizations have also written about potential business conflicts of interest that could be informed by a review of Trump's tax returns. Yet on Tuesday, the House Ways and Means Committee rejected a Democratic effort to obtain the tax documents from the U.S. Treasury Department.

“Until we see his taxes, we don’t know how much money he owes Russia, China and other countries. If Trump won’t voluntarily release his taxes, Congress must force him to do it, as a matter of moral urgency, Constitutional necessity and national security,” said Ben Wikler, Washington director of MoveOn.org.

During the campaign, Trump frequently said he was not releasing his returns because they were under audit. Yet Richard Nixon released his returns despite an audit, and Trump also declined to release prior returns that were not under audit. The Internal Revenue Service has never confirmed whether they are indeed under audit and when it might conclude.

Days after his inauguration, Kellyanne Conway, a top adviser, said he wasn’t going to release his returns because the American people “don’t care.” According to a January ABC News/Washington Post poll, 74% of respondents said he should release his returns, including 53% of Republicans.

The march is another burst of the activism that’s been a regular occurrence since Trump’s inauguration. A day after he became president, millions took to the streets of major cities in the United States and abroad, while protesters have flooded town hall meetings of Republican lawmakers including Reps. Jason Chaffetz of Utah, and Diane Black of Tennessee. Throughout the month of February, the pro-abortion rights group Planned Parenthood is planning 300 events, many of them around the congressional recess that begins Thursday.

Others have targeted Trump's travel ban targeting Muslim-majority nations and there is even a regular protest group on Tuesdays that targets the offices of U.S. senators, including Pat Toomey of Pennsylvania and Colorado's Cory Gardner.

The tax event will be the next big nationally coordinated event. Much like the women’s march was started by a Hawaii grandmother on Facebook, the Tax Day event was conceived on social media by a citizen, New York comedy writer Frank Lesser, on Twitter.

The march will also seek to highlight inequality in the tax code whereby millionaires and billionaires use tax loopholes to pay a lower rate of tax than their workers, according to organizers. The main march will begin in Washington at 11 a.m. in front of the U.S. Capitol and proceed to the Trump Hotel at the Old Post Office. Trump’s deal with the General Services Administration to operate the hotel in that building states that the lease cannot be held by an elected official. Marchers will also pass the IRS building.